Calculating Inductance for Laminated Iron Core Coils—Formulas and Parameters

Hi, I have found many ways and tools (even in this page) to calculate air core or iron core coils, but in the specific type of iron core laminated coils I couldn't find anywhere the way to calculate it.

Anyone could help?

Thanks in advance.

What exactly are you trying to do design an inductor? Your question is confusing. Provide a specific example
so that perhaps someone can help you.

Ok, I will give an example.

I need to calculate an inductor of 10H 400mA for low frequency.

1 step => I need to choose which type of EI core I use.
2 step => I need to calculate the thickness of the sheet pack (bobine size)
3 step => I need to calculte the number of turns and wire diameter
last step => calculate the air gap.

I hope now it is more clear.

OK yes now I see. Yes with specific applications you can determine that. I can't speak to the application on this web site. Now in general, there are various web sites that sell inductors pre manufactured or custom so getting something close to what you need should not be a problem.

Calculating what you have described is also not an issue if one understands magnetics design ( I do). although there are more parameters than what you have outlined. Usually you have to pick a few things then some, "auto," calculator picks the rest for you. Again generally getting an inductor close to what you need isn't a big problem.

You mentioned laminations which is a 50/60 Hz (low frequency) type, then you mention gap. Laminated inductors don't have gaps generally but it is possible.

You should send this request to the web admin for help if you want to stick with this web site. Otherwise send your specific requirements and I can point you in the right direction.

Shure the core is important to the effeciency of the transformer and geometry plays a role- A ring transformer is more efficient then "regular"plates transformer because it is round and therefor flux "friendlier" (less flux resistance).
By the the plate transformer the flux has to pass trough longer way. I remeber from study time that flux resistance is as current resistance in direct proportion to the lengh of the lenge it travels.
Accually i think this forum is not the right place to disscus this since it deals more with electronics. The electricians would know much more about it since they deal with high current and power and there each promil of % place a bigger roll then to an engineer that should provide energy to a pic microcontroller.There are on the net Electrician forums these people would know more.

The actual calculator, isn't the issue, it is the rules it's based on.

I WOULN'T GO TO GOOGLE TO DESIGN MAGNETICS, SERIOUSLY, SERIOUSLY.

There are plenty of companies whose bread & butter (hope you folks understand what that is?) who have exactly what you need. Google's bread & butter isn NOT inductor design. I suppose you would go there to get your teeth fixed, have a brain tumor removed? Perhaps you would. Sane people wouldn't.

Maybe there there is something about laminated coils, If i understand you right by laminated you mean each turn is seperated from the nest and previous with any soort of isolation other then "lackeur"? I do not belive any kind of laminating changes much the permability µ (magnetic character) of the coil.

http://www.coolcircuit.com/tools/single_layer_coil_calculator/
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indcur.html
http://www.eclecticsite.be/calc/awgconverter.htm
http://www.datavoyage.com/coilmaestro/
http://www.66pacific.com/calculators/coil_calc.aspx

No, laminations mean the steel plates that make up the core. They are separated to minimize eddy current losses, similar to resistance losses. Do a Wiki lookup on magnetic eddy current for more info.

Here is something to keep in mind. Anything you do to the geometry of an inductor, changes the inductance. Inductance calculations are all based on geometry and proximity. How much it changes, well that depends, but inductance is all about geometry. It's about magnetic domains as well, so I know someone will throw that one in the discussion.

Unless this inductor or transformer is low frequency say like 50/60/1000 Hz, you really don't need a laminated core structure.

I will try to explain myself better.

I got the following notes for doing the calculation by myself ( I got them from a very old french magazine, september of 1970) and I would like to find something similar and more recent.

http://dl.dropbox.com/u/21405090/materiel%20magnetique.pdf

OK I looked at the document. I don't speak French but that doesn't matter. The information indicates that with a given core selection, and a given number of turns, on that structure which includes the winding bobbin of course, you get a specified nominal inductance.

These sorts of charts I have used many times to design inductors. So what is the issue? It clearly indicates inductance vs other parameters like core size. It also makes mention of a term call Al (cap-A, small-l) which has units of Inductance vs Turns squared.

For Instance one entry indicates 1mH/1000N^2, (1-milli-Henry/!000 turns squared). Perhaps that confuses you.

What that means is if you have that core and you put 1000 turns on it you get 1-mill-Henry of inductance. So what if you want 5 mH, what do you do? Ah that is easy, use the formula.

Turns required = Square root (L-desired/ Al) = SR(L-desired/(1-mH/1000-squared)), or more simple,

N required = 1000*SQ(L-desired) , units are in milli Henry.

Example say I need 5 mH, and a I choose a core that has has an Al of 1mH/1000-squared, how many turns do I need.

Answer: N-required = 1000*SQ(5) = 2,236 turns.

Now for iron core an Al value of 1mH per 1000 turns is very very low in fact it might be as high as 1H/1000 Turns squared. In any event calculating the inductance comes down to using the Al formula, that simple it really is.

If you still can't get that please explain.